Laminated products and adhesive



Reissued Jan. 15, 1952 LAMINATED rn'onuc'rs ann'annssrva" comrosmons ornames 01mm J. Mighton, Madelyn Gardens, DeL, assignor to E. I. du Pontde Nemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing.

1'1, 1951, Serial No.

Application for reissue October Original No. 2,561,215, dated July626,160, November 1,1945.

20, 1951, Serial No. 252,407. In Canada June 11, 1945 13 Claims.

Matter enclosed relssuo specification;

This invention relates to novel compositions and their use as adhesives.particularly in the bonding of textile material to rubber and otherelastomers. The term elastomer" is a generic term for all substanceshaving the properties of natural rubber, reclaimed rubber and artificialrubber-like materials which are ordinarily termed synthetic rubber."

This application is a continuation-in-part of my copending applicationSerial No. 543,202, filed July 1. 1944. now abandoned.

Many compositions have been suggested for use in the art of lamination,including combinations of rubber latex or reclaimed rubber dispersionswith resinous materials. However, in certain types of lamination such asthe bonding of rayon to rubber in the making of rubber tires and thelike, and the bonding of rubber to metal, the adhesives heretoforesuggested for use have not been completely satisfactory and, in the artof lamination generally, there is considerable room for improvement withrespect to the type of adhesive to be used. There is special need forimproved adhesives in the bonding of synthetic fibers such as viscoserayon and nylon fibers to rubber and the like in order to effect atenacious bonding between the fibers and rubber, both at normal and atelevated temperatures It is an object of this invention to provide newand improved compositions of matter. A further object of the inventionpertains to the production of improved adhesives. A special object ofthis invention is concerned with improving the adhesion between rayonand nylon cords and fabrics to rubber, particularly in the manufactureof reinforced rubber structures such as tires. Other objects will appearhereinafter.

The objects of the invention have been attained by the discovery of newcompositions comprising blends of copolymers of vinyl pyridines anddiene hydrocarbons, with heat convertible phenol-aldehyde resols. Inutilizing the new compositions for lamination, the blend of copolymerand thermosetting resol is preferably prepared in an aqueous system, isapplied to the surface of at least one of the objects to be adhered, thetreated surface is brought into contact with the second component of thelamination and the resulting composite article is treated to convert theresin to the infusible state. Where the new adhesive compositions areused in the manufacture of rubber tires, they are preferably applied tothe tire fabric, the rubber stock being then combined with the fabricand subjected to vulcanizing conditions, the resin being converted In hy br k 1 l pears in the original patent but forms no, matter printed initalics indicates the additions made by reissue. I

at the vuicanizingtemperature over to the infusible state.

The following examples illustrate preferred modes of applying theprinciples of the invention and parts, proportions and percentages areby weight unless otherwise specified:

EXANIPLE I A mixture of '75 parts of butadiene and 25 parts ofalpha-vinyl pyridine is emulsified in 157 parts of an aqueous solutioncontaining 4 parts of sodium oleate, 0.5 part of sodium hydroxide, 1part of a formaldehyde/sodium naphthalene sulfonate condensationproduct, 1 part of potassium persulfate and 0.1 part of potassiumferricyanide. One half /z) part of lauryl mercaptan is added and theemulsion is heated for twenty hours at 40 C. in a sealed, glass linedvessel equipped for efficient agitation. The resulting smooth latex istreated with an antioxidant consisting of 2 parts of aphenyl-alphanaphthylamine and diphenylamine (55:45) mixture dispersed inwater. The dispersion contains about 40% solids.

One hundred ten parts of resorcinol and 225 parts of a 40% formaldehydesolution are dissolved at 25 C. in 475 parts of water to give a 25%resol solution.

adhesive loading, 1. e. per cent dried adhesive on the basis ofunimpregnated fabric, and placed adhesive side down on an unvulcanizedbut compounded natural or synthetic rubber stock. Formulas for thestocks used may be found in the appended Table IV. The composite isplaced in a mold and heated at to C. until the rubber is vulcanized andthe adhesive is heatconverted. The composite is then removed from [them]the mold, cooled and the bond strength determined by measuring the pullin pounds per examples following are shown in Table I. As a cinol, 0.3part of sodi basis for comparison, a conventional blend of rubber latexwith a resorcinol/tormaldehyde resin gives, in this test, bonds betweenrubber and vis- Examp cose rayon-or nylon of about20 pounds lltgi it 7at 25 C;:and pounds per inch or less a Included in Table I to illustratethe superiority 01 EXAMPLE V the butadiene/vinylPyridinecopolymer-resorcipyridine "latex, prepared as described in A ofaqueous solution of sodium dibutyl dithiocarbam 1.2 parts of sodiumhydroxide and 90 parts'of a substituting isoplene for butadiene and oyanadhesive for bonding rubber to nylon and to 25 100 parts of er id 1 Pa01 a 50% rayon tsdesm edmc'or Example I. The results aqueous Solution Osodlum dllflltyl dlthiot e ggto shown i g 5 of T l carbamate with partsof resorcmol, 30 parts I; bonds'of and 16 pounds per inch at 25 and 0faque us formaldehyde solution, and 0.3 100 C. res 'ectively wereobtained between viscose part of. sodium hydroxide and 100 parts 01'water rayon a bber with 11% adhesive loading. is tested as an adhesiveas described in Example 7 I v I-C. At 8% adhesive loading, bonds as highas s pounds per inch and 100 pounds per inch Able'n'dlot IOO'parts oif'a90/10 butadiene/vinyl are obtained between nylon and rubber and apyridinezfiatex prepared in a manner similar to j /25 butadiene/styreneinterpolymer respecthat o the 75/25 compositionin Example I-A, 35 tivelyat 25 C. At 100 C., the adhesion exceeds 100 partsof water and v1' part01:50:95 aqueous the tear strengths of the elastomer vulcanizates.

" v TableI BONDING 0F NYLON FABRIC TO RUBBERS Loam Average Bonds,

Resorcinol/iormaldehyde resin (Ex- {Rubber ple LB). o -s..

g 1 Lbs/Inch atv Rubber in: f I Adhesive Stock Per a- {3if;; .1112

3: $8 38 unczruuon 75/25 butadiene/vinyl pyridino-resorci- {Rubbcr jnol/formaldehyderesin (Example II). G

- 6 .90/10 butadleue/vinyl pyridine-resorci- {Rubber moi/formaldehydere5in'(Example 111). GR

' v7 /15 butadlene/vinyl pyridine-rosorcinod/formaldehyde resin (ExampleG 8 /5 butadlcne/vinyl' pyridine latexresorcinol/lormaldehyde resin(ExameV.

9 70/30 'butadiene/acrylonitrilei latexresorcinol/formaldchydc resin(3/1).

75/25 butadiene/styrene lotcx-rcsorcinol/(ormaldchydn resin (2/11.

j 11 'Po1ychloroprcnelatox-rcsorcinol/Iorniul- --t'dehyderesin (2/1).

- d'Ri-sis a commercial synthetic rubber composed approximately of a75%-25% butadiene/styreneinterpolymer prepared according to U. S. PatentNo. 1,938,731.

I {No maasurablcbondat1001C.

' 'No adhesive failure; rubber stock tore.

' v Examples I jtoVI are concerned with the use, .t0gether with re'sols,of copolymers of dienes and alphav'inyl pyridine (2-vinyl pyridine)which 6 hasthe structural formula:

/1 "go "GH sodium.'dibutyl dithioea arn'a 8 u 'ene/vinyl ct w' r p 'paed as described inch necessary to separate'the fabric and the in ExampleLA for the 75/25 composition, rubber. The results of this test and oftests 01' parts or water and 1 part of 50% aqueous sodium similaradhesive compositions described in the dibutyl dithiocarbamate with 15parts of resorum hydroxide, 30 parts of 37 aqueous formaldehyde solutionand 100 parts 01" water is tested as an adhesive as described i..1 1eL0. The results are shown in Table I.

v "A blend of a 95 5 butadiene/vinyl pyridine in blend as an adhesiveare a 15 25 butadiene/styrene P1Ymer1ateX Prepared as in Example I-Awith interpolymer, 70/30.ibutadiene/acrylomtme a resorcinol/formaidehyderesin is made as in Example IV and tested as an adhesive. The bonds ymFP 1P h 9 latgx' Y obtained are shown in Table I. item 8.

" Exxmmn of -i00parts=of a 75/25 bu'tadiene/vinyl E AMPLE VI 7 I g artsof water and 4 arts of a 507 A blend comprising 100 parts of a 26% latexExample 400 p p o 20 of a 90/10 isoprene/vinyl pyridine copolymer preatewith, 44 parts or resorcmol' parts of water pared in a manner similar toExample LA, by

37% aqueous formaldehyde solution is testedas 1118 Polymerization cycle0f 40 hours at The following examples are directed to copolymers ofdienes and -ethyl-2-vinyl pyridine, together with resols, this form ofthe invention being found to give excellent results. 5-ethyl- 2-vinylpyridine has the structural formula:

5-ethyl-2-vinyl pyridine may be prepared as follows: 5-ethyl-2-methylpyridine (collidine) is prepared from paraldehyde and ammonia in amanner similar to that described in British Patent No. 146,689 andGerman Patent No. 349,184. By the treatment of 5-ethyl-2-methyl pyridinewith formaldehyde according to the methods employed by Loiiler andGrosse (Berichte 40,1325; 1907) for preparing 2(beta-hydroxyethyl)pyridine from alpha-picoline, 5-ethyl-2-(beta-hydroxyethyl) pyridine isformed, this latter compound being dehydrated to 5-ethyl-2-vinylpyridine by distillation from solid sodium hydroxide in a manner similarto that described by Ladenburg (Berichte 22, 2585; 1889) for thedehydration of 2(beta-hydroxyethyl) pyridine to 2-vinyl pyridine.

nxxmmnvn One (1) part of dodecyl mercaptan is added and the mixture in asealed glass container is agitated end-over-end for sixteen hours in awater bath maintained at 40 C. The resulting smooth latex, containingabout 35% solids, is treated with antioxidant consisting of 3 parts ofphenylalpha-naphthylamine and diphenylamine (55 :45) mixture dispersedin water.

A blend of 20 parts of the 90/10 butadlene/ 5-ethyl-2-vinylpyridinecopolymer latex described above and 20 parts of distilled water, with asolution of 2 parts of resorcinol, 1 part of a 37% aqueous formaldehydesolution, 1.1 parts of an aqueous sodium hydroxide solution and parts ofwater, is applied after aging at room temperature for twenty hours to astrip of a square-woven nylon fabric, one inch wide and five incheslong. The impregnated fabric is dried ten minutes at 135 C. and placedadhesive side down on an unvulcanized but compounded natural orsynthetic rubber stock. Formulae for the stocks used may be found in theappended Table IV. The composite is placed in a mold and heated under150 pounds per square inch pressure until the rubber is vulcanized andthe adhesive is heat-converted. The composite is removed from the mold,cooled, and the bond strength determined by measuring the pull in poundsper inch necessary to separate the rubber and the fabric. The results ofthis test and of tests of similar adhesive compositions described in theexamples following are shown in Table II.

EXAMPLEVIII Item 3 in Table II shows the results of similar tests of ablend of an 80/20 butadiene/5-ethyl- 2-vinyl pyridine copolymer preparedin a manner similar to Example VII-A, with the sameresorcinol/formaldehyde resol in the same copolymer to resol ratio.

Item 4 in Table II shows the results of similar tests with a /25butadiene/5-ethyl-2-vinyl pyridine copolymer in the same copolymer toresol ratio as in Example VII and with the same resol.

EXAMPLE IX A mixture of 48 parts of isoprene and 12 parts of5-ethyl-2-vinyl pyridine is emulsified in 96 parts of an aqueoussolution containing 2.4 parts of sodium oleate, 1.2 parts of sodiumrosinate, 0.48 part of sodium hydroxide, 0.6 part of aformaldehyde/sodium naphthalene sulfonate condensation product, 0.6 partof potassium persulfate and 0.09 part of potassium ferricyanide.Six-tenths (0.6) part of dodecyl mercaptan is added and the mixture, ina sealed glass vessel, is agitated end-over-end for thirty-six hours ina water bath maintained at 40 C. The resulting smooth latex, containingabout 35% solids, is treated with an antioxidant consisting of 1.8 partsof a phenyl-alpha-naphthylamine-diphenylamine (55:45) mixture dispersedin an equal weight of water.

A blend of 20 parts of the /20 [is] isoprene/5- ethyl-2-vinyl pyridinecopolymer latex described above and 20 parts of water with a solution of2 parts of resorcinol, 1 part of a 37% formaldehyde solution, 1.1 partof an aqueous 10% sodium hydroxide solution and 20 parts of water isapplied to nylon fabric and tested as an adhesive exactly as describedin Example VII. The results are shown as item 5 in Table II.

EXALEPLEX A mixture of 51 parts of butadiene, 9 parts of 5-ethyl-2-vinylpyridine and 12 parts of carbon tetrachloride is emulsified in parts ofan aqueous solution containing 2.5 parts of the sodium salt of sulfatedmethyl oleate,.0.6 part of a formaldehyde/sodium naphthalene sulfonatecondensation product, 0.3 part of sodium hydroxide, 0.6 part ofpotassium persulfate, and 0.09 part of potassium ferricyanide. Themixture, in a sealed glass container, is agitated end-over-end fortwenty hours in a water bath maintained at 40 C. The resulting smoothlatex, containing about 30% solids, is treated with an antioxidantconsisting of 1.8 parts of phenyl-alpha-naphthylamine and dlphenylamlnemixture (55:45) dispersed in an equal weight of water.

above and parts of water with a solution of 2 parts of resorcinol, 1part of a 37% formaldehyde solution, 1.1 parts of an aqueous 10% sodiumhydroxlde solution in parts of water is applied to mrlon fabric andtested as an adhesive exactly as described in Example VII. The resultsare shown as item 6 in Table II.

The composition described in Example X-C above was evaluated in the sameway as an agent for bonding viscose rayon to rubbers. The results areshown as item 8 in Table II.

EXAMPLEXI Twenty-five parts of the 85/ 15 butadiene/ 5-ethyl-2-vinylpyridine copolymer (isolated from the latex of Example VII-A by theaddition of a suitable coagulant such as ethyl alcohol or an aqueoussolution of acetic acid and sodium chloride, followed by washing thecoagulum and drying it on a rubber mill) is dissolved with stirring in amixture of 225 parts of xylene and parts of methyl ethyl ketone. To 25parts of the resulting smooth cement, a solution of 1 part of athermosetting resin and 1 part of a solution 01' an accelerator for theresin setup, both in 10 parts of butanol, is added and the viscouscement is applied to fabric, dried and vulcanized to rubbers asdescribed above. The bonds obtained are shown as item 9 in Table II.

Table III BONDING OF NYLON FABRIC TO RUBBERS [Adhesive Loading: of 7% to10%.]

The following examples illustrate the improved eflect obtained byutilizing a blend of natural rubber with a diene/ vinyl pyridinecopolymer and a thermosetting phenolaldehyde resin.

EXAMPLEXII A mixture of 90 parts of butadiene and 10 parts of 2-vinylpyridine is emulsified in 157 parts of an aqueous solution containing 4parts ol sodium oleate, 2 parts of sodium rosinate, 0.5 part of sodiumhydroxide, 1 part of a formaldehyde/sodium naphthalene sulfonatecondensation product 1 part of potassium persulfate and 0.1 part ofpotassium lerricyanide. One and onehalf (1.5) parts of lauryl (dodecyl)mercaptan are added and the emulsion, in a sealed glass container, isagitated in a pressure vessel for twenty hours at 40 C. The resultingsmooth latex is treated with an antioxidant consisting of 2 parts 01' aphenyl-alpha-naphthylamine and diphenylamine (:45) mixture dispersed inan equal weight of water. The dispersion contains about 38% solids.

A solution of 3 parts of resorcinol, 1.6 parts of 37% formaldehydesolution and 1.65 parts of an aqueous 110% sodium hydroxide solution in30 parts of distilled water is added slowly, with stirring, to apreformed mixture of 4.5 parts of concentrated natural rubber latexsolids), 22.5 parts of a /10 butadiene/Z-vinylpyridine copolymer latexprepared in a manner similar to that of Example XII-A, and 33 parts ofdistilled water.

This blend is applied by dipping and squeezing to a strip ofsquare-woven nylon, the fabric is dried ten minutes at C. and placedadhesive side down on an unvulcanized but compounded natural orsynthetic rubber stock Formulas for the stocks used may be found in theappended Table IV. The composite is placed in a mold and heated underpounds per square inch pressure until the rubber is vulcanized and thead- Rubber Adhesivc stock Average Bonds,

Lbs

.lInch at ubber... RS

Rubber. GRS

Rubber..-

Rubber... 0

ridine eopolyyde resin (Exgs as 21:; s e s as as gs as :r as a;

1 indicates failure 0! stock rather than adhesive.

The"'greenf (uncured) adheslonto rubber of the composition above isshownby manual testto be far better than. that of a simiiaricompositionwithout-the naturel rubberlatexa The following test is used to obtin-endowmentsurements. of "green". .adhe'eien the examples" below: Theadhesive-composition A plied to a 8 inch by 2 inch nylon fabric and thecoated-material dried-iin' an i oven for from five minutesat.100"-Qftoten minutes at 185' C. This, impregnated-materials allowed to cooland is then appliedto a 1 inch by 1.5 inch strip of uncured compoundedrubber stock from which a [hollaridII-{olldfid cloth protective coatinghas Just been removed; after warmin: the stock to 100 C. A thin glasscover is placed on the fabric andthe assembly pressed together while therubber stock cools, under a five pound pressure for-five minutes. Theweight and cover glass are then removed. the fabric-rubber laminate agedsixteen hours and the pull required to separate the rubber and fabricmeasured in grams per inch.

EXAMPLE XIII In a manner similar to that of Example XII-B, 70:25, 50:50and 40:60 mixtures (on a dry basis) of a 90/10 butadiene/2-vinylpyridinecopolymer prepared in the manner of Example XII-A and natural rubberlatex were blended in a proximately a 8:5:1 ratio of total rubber-:resinformers with a 1/0.7 (molar) resorcinol/formaldehyde resol prepared bymixing the ingredients as described in Example XII-B. The resultingadhesive compositions were tested in-exactly the man- 10 ring, to apreformed blend of 12 arts of natural rubber latex concentrate (1095olids), 13.3 parts of an 85/15 butadiene/2-vinylpyridine copclymer latexcontaining about 40% solids and prepared in a manner similar to that ofExample XIII-A, and 25 parts of distilled water. I

The resulting composition is tested exactly as described in Example XIIas an agent for bonding nylon fabric to rubbers. Cured bonds at C. ofover fifty pounds per inch between the fabric and Git-S or rubber wereobtained. At 95 0., the adhesion exceeded the tear strengths of thevulcanizates.

The "green" adhesion of this composition is.

demonstrated by manual tests to be fully equivalent to thatoftheadhesive based on the 60/40 blend of natural rubber and the 90-10butadi- -.'ene-vinylpyridine copolymer of Example XIII -.(Tab1e .II I,item' a). The "green" adhesion of a I controla 'esive made up accordingto Example IV I is markedly inferior and is about equivalent to that ofitem 5 in Table III.

emu: xv

A solution of 2.8 parts of resorcinol, 1.8 parts of 37%.formaldehydesolution and 1.1 parts of aqueous-110% sodium hydroxide solution inparts-of water is added slowly, with agitation,

to a preformed blend of 12 parts of concentrated natural rubber [later]later (60% solids), 18 parts of the 85/15butadiene/5-ethyl-2-vinylpyridine copolymer latex prepared as describedin Example X-A, and 20 parts of water. The resultin: composition isapplied to nylon fabric and tested for both cured and green adhesion asdescribed in Example XII. The green adhesion is equivalent to that ofitem 4 in Table III. The cured bond between nylon fabric and rubber isover fifty pounds per inch at 25 C. and exceeds the tear strength of therubber at 95 C. The bond to GR-S exceeds the tear strength of thevulcanizate at both 25 and 95- C.

A control adhesive made up as described in Example X without naturalrubber latex, gives 1 equally excellent cured bonds, but the greenadhesion is inferior, approximately equal to that of item 5 in TableIII.

Table III ADHESION OF NYLON FABRIC T0 RUBBERB Cured Adhesion, LbJIn.

Green Adhesion Adhesive To Rubber To GR-S To Rubber,

GJIn. at 25 l 77 Butadicns/vinylp rldine ccpolymer (90/10); 28 I 10Better than control 23 natural rubber p us resorcinol and iormaldo-(Item 5). hyde (Example X11). .2 75:25 blend (Example XIII) 42 60 I 26245. 6 60:50 blond EExample XIII] 40 32 01 1 32 B50. 4 40:00 blendExample XIII) 48 38 55, 2) 2,700. is 00/10 hutadlone/Z-vinylpyridineplus resorcinoll 46 35 23 150.

formaldehyde resol. 0 Rubber lotex(resorciuni formaldehyde resnl... l810 45 20 8,000.

1 Indicates failure 01 cured rubber em Failure, at least in part, ofuncured ner described in Example XII for both "green" and curedadhesion. The results are shown as items.2.'8 and 4 respectively inTable III.

EXAMPLE XIV solution of 2.3 parts of resorcinol, 1.7 parts of a 87%formaldehyde solution and 1.1 parts of aqueous 10% sodium hydroxidesolution in 25 parts of distilled water is added slowly. with stir- (krather than adhesive.

rubber stock rather than adhesive.

The following example is directed to copolymers of2-methyl-5-vinylpyridine and a diene. togetherwith resols:

EXAMPLE XVI 2-[methylJMethyl-5-vinylpyridine (a methylsubstitutedbeta-vinylpyridine) is prepared by treating 5-ethyl-2-methylpyridinewith chlorine,

5 treating the resulting fi-(alpha-chloroethyl) -2- A mixture of 45parts of butadiene, parts of' 2-methyl-5-vinylpyridine and 1.2 parts ofrosin is emulsified in 80 parts of a solution prepared by dissolving15.6 parts of sodium hydroxide. 8 parts of oleic acid, 12 parts offormaldehyde/sodium naphthalene sulionate condensation product and 12parts of potassium persulfate in 1,500-

parts of water.. To this emulsion is added.0.09

part of potassium'ferricyanide and 0.6 part'of" twenty-four hours in awater bath maintained at 40 C. To the resulting smooth latex,containing" about 40% solids, is added 1.8 parts of a'phenylalphanaphthylamine diphenylamine (:45)

mixture in the form weight of water.

A solution composed of 2 of a dispersion in anlequal parts ofresorcinol, 1.7

parts of a 10% aqueous soluion of sodium hydrox-' ide, 1.05 parts of 3720 parts of water is ylpyridine copolymer dispersion prepared asdescribed above. The blend is diluted with 20 parts of water. Afteraging for twenty-four hours at room temperature, the blend is applied toa nylon fabric and tested as an adhesive, as described v Table IVELASTOMER CARCA'SS STOCKS EMPLOYED FOR BONDING a Rubber Git-S SmokedSheets 100 R-B I00 Zinc Oxide 50 5 Channel Black. s. 32Phenyl-beta-napthylamine 1. 50 Pbenyl-alpha-naphthylamine r l. 00 Sulfur2. 1. 50 Btcnric Acid. 2. 00 2. 00 Pine Tar 2. A petroleum distillate(Light Process 0il) 3.00 Mercaptobenzthiazole 0. 75 N-cycloherylbenzthiazyl sulphenamidc 1. 30

aqueous formaldehyde, and" added slowly, with stirring, to 20 parts ofthe 75/25 butadiene/2-methyl-5-vim- .thejse m mottin "was 1 ien'e'rallyreslnofls polymerizable hydrocarbon' dienes dodecyl mercaptan.Theemulsion is sealed ina q glass container and rotated end-over-endforv prene, dimethylbutadiene"orpiperylene because of theirlowcos't'a'nd availabili r i ticula'rly in bonding fabrics and anyphenol aldehyde heat convertible resol.

By phenol-aldehyde. heat ,wn emm vresa: is vmeant'anygcondensation-product.ofjan dehyde un er. lie-infi with h rm neiab se lvh esize ccmprehends, P i i /d am propy'i-2-vinyl: pyridine, sbutyaavmy syrnme ridine are preferred.- The'invention ontempla'tesforuse in the prep-' aratio'n': of yinylpyridine/dieneflhydrocarbomco-'particularly Polymers any; diene hydrocarbon,

7 r-c'onta conJugated double bonds, .e. g.' '1',-3'-,buta' because ofthe] readiness with] which polymerize with vinylpyr'idines to-"g'ivf vpossessing optimum adhesive 1 characteris't Thediene va'ried'over widelimitsi most purposes, parto rubbers-a pliable compositionhavingrubber-like characteristics is preferred. Good results areobtainedwith copolymers mwhichr'jao /t to 97-%iof"the total,is

diene hydrocarbon; in 1 general, E those products consisting of ,to@70e%diene and the remainder a vinylpyridine.are preferred. Three componentcopol'ymer's' eontaining'atleast %;,jdiene Y and 5%101' avinylpyridine-the remainderf'con-=-f'".' sisting of other vinyl or.vinylidene compoundsor 'butenedloic acids oresters, such as styrene,di-p] I methyl (vinylethinybj carbinol, vinylidene chloride, methylvinyl; lr'etone." vinyl naphthalene methyl,methacrylatefacrymnitrile ordiethyl fut-1. Q inarate and the like-areaiso operable and are in- Ieluded.

m; formingflthe dieneffhydrocarbonwinylpyrief,

dine copolymer, a pH preferablyin excess of 7.0

is used, the pH at the. beginning of: ;the,copo lymerizationpreferably'jeing 10.0 12.0. .,Aj1s"o,f*' I although it is preferred touse the aqueousemulsion method for forming? the diene hydrocar--bon/vinylpyridine ,cop'o'lymer, one may dissolve the monomers and effectthereaction in solution,

-or one may merely; the monomers in bulk (without solvent 'or'dispersing. medium) and cause the reaction to proceed. Example "1,-Aillustrates a typical-method forpreparing the copolymer in an-'aqueous'medium, but the conditions can,ofcourseibejvariedinaccordancewith the knowledge of thoseskilledin theart. ,j'.

It will be'understood however that the invention is not limited as tothe manner orconditions'of preparing the diene-vinylpyridine copoly- I"The inventionf broadly comprehends blends of any vinyipyridine/dienehydrocarbon copolymer f n byridmeprsr I hydrocarbonzvinylpyridine ratioat the copolymer 'operable'inithis invention can be nor. Thus, in placeof sodium oleate, one may use other alkaline dispersing agents such asalkali may use other well known protective colloids.

While emulsion systems are in general preferred for convenience inpreparing aqueous adhesive formulations, one may use bulk, solution orgranulation polymerization techniques. Suitable polymerizationinitiators or catalysts include peroxides such as benzoyl peroxide,lauroyl peroxides and hydrogen peroxide, inorganic percompounds such asalkali metal perborates and persulfates, potassium persulfate being thepreferred polymerization initiator. -In place of potassium ferricyanidewhich functions to activate the catalytic action of the potassiumpersulfate used in the examples, one may use other catalyst activatorssuch as alkali metal ferrocyanides and readily oxidizable sulfoxycompounds such as sodium hydrosulfite, sodium bisulflte, sodiumpyrosulilte and the like. Where an organic peroxide such as benzoylperoxide is used, activators are normally not used.

The use of modifiers such as carbon tetrachloride, 5,5,5-trichloroamylmercaptan and long chain unsubstituted mercaptans such as the laurylmercaptan (dodecanethiol) of Example I-A, octyl and decyl mercaptans orother commercially available mercaptans predominating in octyl, decyiand higher mercaptans, dialkyl xanthogen disulfldes, sulfur and othermodifiers, is optional in the polymerization mixture, but is preferredbecause of the improved green adhesion or ability to hold the laminationsecurely in place before the rubber stock is cured.

The polymerization [temeprature] temperature may be varied within widelimits, for example 0" to 100 C., but in general tempera tures of to 60C. are preferred. The time required to obtain a high yield ofpolymerizate will depend on the temperature, catalyst and system,

may be much greater or less than twenty hours, a shorter periodordinarily being used where the reaction is carried out at the highertemperatures.

The smooth latex resulting from polymerization may be stabilized in anyconvenient manner. The addition of an aromatic amine, preferably in theform of a dispersion, e. g. phenyl alpha-naphthylamine or thephenyl-alpha-naphthylamine-diphenylamine of Example I-A, serves tostabilize the rubber in the latex or aqueous dispersion until it isready to be used.

In place of formaldehyde, there can be used for the preparation of theheat convertible resols other aldehydes and materials which, under theconditions of reaction, liberate formaldehyde in the preparation of thethermosetting aldehyde resols. Examples of such materials are paraformaldehyde, hexamethylenetetramine, acetal dehyde, butyraldehyde,chloral, furfural and salicylaldehyde; formaldehyde, or materials whichreadily liberate formaldehyde, are preferred.

.e. g. emulsion system, used. The reaction time The phenols used for thepreparation of the thermosetting aldehyde-phenol resol can be monohydricor polyhydric phenols or mixtures of these. Examples of monohydricphenols are phenol, the cresols, the xylenols and the naphthois, andtheir condensation products with aldehydes or ketones, e. g.diphenylomethane or diphenylolpropane; halogen, or alkyl-substitutedphenols such as chlorophenols, tertiary-butyl phenol and tertiary-amylphenol. Examples of polyhydric phenols are resorcinol, catechol,phloroglucinol, orcinol and hydroquinone as well as natural productscontaining polyhydric phenolic groups such as quebracho extract. Thepreferred phenols are the mononuclear polyhydric phenols, particularlyresorcinol, since they provide, in general, superior adhesion.

The particular resins most useful in the practice of the invention areheat convertible resorcinol/formaldehyde resols. The thermosettingresorcinol/formaldehyde resol may be made of mixtures havingresorcinol/formaldehyde mol' ratios of from 3:1 to 1:10. In general,those containing about 0.7 to three mols of formaldehyde per mol ofresorcinol are preferred. Aldehyde liberating substances such ashexamethylenetetramine may be employed to replace part of the aldehyde,but, in general, it is preferred to operate without them.

The inclusion of rubber latex, together with the diene/vinylpyridinecopolymer and thermosetting resol is of particular advantage in view ofthe excellent adhesion effected by such compositions before curing ofthe rubber ("green" adhesion) as well as good final (cured) adhesion.Any good quality natural rubber may be used for this purpose, Hevearubber latex. either normal, dilute or concentrated, being preferred forthe preferred aqueous adhesion systems.

The amount of natural rubber latex used in admixture with the copolymer,depending on the amount of green adhesion desired, may vary from 5% toof the combined natural rubber and copolymer with little or no loss incured adhesion. Compositions containing from 30% to 70% of naturalrubber latex are in general preferred. Amounts below 30% give only minorimprovements in green adhesion over similar compositions without rubberlatex, which improvements are frequently not satisfactory for manyprocessing operations. If more than 70% of natural rubber latex be used,somewhat lower cured bonds will result at the low adhesive loadingswhich give excellent results with compositions containing less naturalrubber. Particularly noteworthy is the large increase in green adhesionobtained by increasing the amount of natural rubber from 50% to 60%(items 3 and 4 in Table III), almost up to the level of compositionscontaining only rubber latex with the resorcinol/formaldehyde resin.This great increase in green adhesion is made without any serious lossin cured bond strength over the 50:50 natural rubber/copolymercomposition, or even over compositions containing only copolymer,resorcinol and formaldehyde, which is a surprising and unpredictableresult.

In the practice of this invention, blends of the dienehydrocarbon/vinylpyridine copolymer and the resin containing from 10% toresin may be employed. In general, for tire cord apolication, it ispreferred to operate within the range of 20% to 60% resin, particularlyfrom 25% to 40% resin. It is also preferred to use the adhesive in thealkaline state, i. e. at a pH above 7.0.

Inaddition to the copolymer, resin, rubber and the other materialsdiscussed above as suitable addition agents, the adhesive compositionmay contain fillers such as carbon black, vulcanizing and compoundingingredients such as sulfur, zinc oxide, rubber accelerators, softeners,plasticizers, tack producing agents other than natural rubber and thelike, suitably dispersed or dissolved in the blend.

The use of an aqueous system for the blending and practical applicationof the adhesive is preferred for convenience and economy. Solutions ordispersions of the copolymer and the resin in suitable organic solventssuch as toluene, toluene-ethyl alcohol mixtures, or chlorinatedaliphatics however may be used.

As illustrated in the examples, the resorclnol! formaldehyde componentor resol may be prepared by the simple solution of the resorclnol andformaldehyde in water or an alkaline material such as sodium hydroxidemay be added for the purpose of advancing the condensation whichproceeds readily in alkaline solution. Alternatively, as pointed out inExample II and other examples, the resol may be formed by adding thephenol and aldehyde to the butadiene/vinylpyridine emulsion as inExample II, preferably in the presence of sodium hydroxide or equivalentalkali. The sodium dibutyl dithiocarbamate used in Example 11 and inother examples functions as a vulcanization accelerator, but itspresence is entirely optional especially since the accelerator in therubber stock in all probability migrates to the adhesive.

The lamination procedure may be varied considerably. Generally speakinghowever, the temperature used for curing the thermosetting resol isabout 100 to 200 C. and where the lamination involves the plying of therubber to other things such as metal, cotton or synthetic fibers forexample, the unvulcanized rubber stock will be vulcanized at atemperature within this range, thereby making unnecessary a separateheating step for converting the resin to the infusible state. By properformulation of the rubber stock and adhesive, the compositions can bemade to laminate at ordinary temperatures. It is preferred that theadhesive be dried as described in Example I-C after its application toone of the elements to be laminated and before the second element to belaminated is brought into contact with the element containing theadhesive. Also, an improvement in bond strength is noted when either theresol solution or the blend of diene hydrocarbon/vinylpyridine and resolis set aside to age for a period before application as an adhesive: asis described in Example VII, this aging period may be twenty hours, buta greater or less period, e. g. one hour up to forty-eight hours may beused with advantage. This aging period is particularly beneficial wherethe resol comprises resorclnol to formaldehyde in the moi ratio of1:0.7.

As will be noted from the above description, the compositions of thisinvention, when used as adhesives, provide an excellent bond not only atordinary temperatures, but also at elevated tem peratures.

While the adhesive is particularly suited for bonding cotton, viscoserayon and nylon fabrics to rubbers such as natural rubber, GRS,neoprene, butadiene/acrylonitrile rubber and other diene copolymerrubbers as in the manui'acturev of tires, belts, coated fabrics andother articles, it may be used in other applications such as bondingmetals, wood, paper, ceramics, glass,

leather or plastics to each other or to rubber.

In view of the great utility of the compositions embodied in the presentinvention for improving adhesion, this phase of the invention has beenparticularly emphasized, but it will be understood that the novelcompositions may also be used generally as film-forming components ofcoating compositions and as binders in molding compositions.

The term "copolymer as used herein signifies a polymer containing in itspolymer molecule units of more than one monomeric material, e. g. thepolymer obtained by polymerizing together both monomeric vinylpyridineand monomeric butadiene; the term is not intended to include physicalmixtures of diiferent polymers.

The practice of the invention is capable of considerable modificationand any variation which conforms to the principles of the invention isintended to be included within the scope of the claims.

I claim:

1. An adhesive comprising a copolymer of a diene hydrocarbon-containingconjugated double bonds and a member of the class consisting ofunsubstituted monovinylpyridines and alkyl substitutedmonovinylpyridines, the said hydrocarbon being present in amounts of 50%to 95% by weight of said copolymer and the vinylpyridine being presentin amounts at least 5% by weight of said copolymer in admixturewith aheat convertible polyhydric phenolaldehyde resol, the amount of saidresol in said adhesive being from 20% to 60% [by weight of saidadhesive] of the combined weights of said copolymer and said resol.

2. An adhesive comprising a copolymer of a diene hydrocarbon containingconjugated double bonds and a member of the class consisting ofunsubstituted monovinylpyridines and alkyl substitutedmonovinylpyridines, the said hydrocarbon being present in amounts of 50%to by weight of said copolymer and the vinylpyridine being present inamounts at least 5% by weight of said copolymer in admixture with a heatconvertible resorcinol-aldehyde resol, the amount of said resol in saidadhesive being from 20% to 60% [by weight of said adhesive] of thecombined weights of said copolymer and said resol.

3. An adhesive comprising a copolymer of a butadiene hydrocarboncontaining conjugated double bonds and a member of the class consistingof unsubstituted monovinylpyridines and alkyl substitutedmonovinylpyridines, the said hydrocarbon being present in amounts of 50%to 95% by weight of said copolymer and the vinylpyridine being presentin amounts at least 5% by weight of said copolymer in admixture with aheat convertible resorcinol-aldehyde resol, the amount of said resol insaid adhesive being from 20% to 60% y weight of said adhesive] 0! thecombined weights of said copolymer and said resol.

4. A laminated article comprising a solid material bonded to a solidmaterial by an adhesive comprised of a copolymer of a diene hydrocarboncontaining conjugated double bonds and a member of the class consistingof unsubstituted monovinylpyridines and alkyl substitutedmonovinylpyridines, the said hydrocarbon being present in aldehyde resinformed from a heat convertible 17 resin previously blended with saidcopolymer, the amount of said resin being from 20% to 60% [by weight ofsaid adhesive] of the combined weights of said copolymer and said resin.

5. An article in accordance with claim 4 in which the said resin is aresorcinol-aldehyde resin.

6. An article in accordance with claim 4 in which a material is bondedto an elastomer by said adhesive.

7. An article in accordance with claim 4 in which a fibrous material isbonded to an elastomer by said adhesive.

8. A laminated article comprising a solid material bonded to a solidmaterial by an adhesive composed of a butadiene/vinyl pyridine copolymerin which butadiene makes up 50% to 95% of said copolymer and thevinylpyridine being present in amounts at least 5% by weight of saidcopolymer in admixture with a resorcinol-aldehyde resin formed from aheat-convertible resin previously blended with said copolymer, theresorcinol/aldehyde mol ratios in said resin being from 3:1 to 1:10 andthe amount of said resin being from 20% to 60% [by weight of saidadhesive] of the combined weights of s id copolymer and said resin.

9. A laminated article in accordance with claim 8 in which saidvinylpyridine is 2-vinylpyridine.

10. A laminated article in accordance with claim 8 in which the saidaldehyde is formaldehyde.

11. In laminates, a composition comprising a copolymer of a dienehydrocarbon containing conjugated double bonds and a member of the classconsisting of unsubstituted monovinylpyridines and alkyl substitutedmonovinylpyridines, the said hydrocarbon being present in amounts of to95% by weight of said copolymer and the vinylpyridine being present inamounts at least 5% by weight of said copolymer in admixture with aninfusible polyhydric phenol-aldehyde resin formed from a heatconvertible resin previously blended with said copolymer, the amount ofsaid resin being from 20% to [by weight of said adhesive] of thecombined weights of said copolymer and said resin.

12. A composition in accordance with claim 11 in which said infusibleresin is derived from a resorcinol-aldehyde resin.

13. A composition in accordance with claim 11 in which said copolymer isa butadiene/vinyl pyridine copolymer and said infusible resin is derivedfrom a resorcinol-formaldehyde resin.

CHARLES J. MIGHTON.

REFERENCES CITED The following references are of record in the file ofthis patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,849,109 Novotny Mar. 15, 19322,128,635 Charch Aug. 30, 1938 2,255,834 Taylor et al. Sept. 16, 19412,277,941 Almy Mar. 31, 1942 2,291,208 Brown et al. July 28, 19422,334,526 Allison Nov. 16, 1943 2,394,375 Gross Feb. 5, 1946 2,402,020Cislak June 11, 1946 2,405,038 Jennings July 30, 1946 2,429,397 Comptonet a1 Oct. 21, 1947 FOREIGN PATENTS Number. Country 1 Date 849,126France Aug. 7, 1939

